1. Field of the Invention
The present invention relates to a power transmission chain and more particularly to a power transmission chain and a power transmission apparatus which are suitable for a continuously variable transmission (CVT) of a vehicle such as an automotive vehicle.
2. Related Art
As an automotive continuously variable transmission, there is known an automotive continuously variable transmission, as is shown in FIG. 6, including a drive pulley (2) having a fixed sheave (2a) and a movable sheave (2b) and provided on an engine side, a driven pulley (3) having a fixed sheave (3b) and a movable sheave (3a) and provided on a drive wheel side and an endless power transmission chain (1) placed to extend between the pulleys, wherein by moving the movable sheaves (2b), (3a) towards and away from the fixed sheaves (2a), (3b) by means of a hydraulic actuator so as to clamp the chain by virtue of hydraulic pressure, so that a contact load is generated between the pulleys (2), (3) and the chain (1) by the clamping force so as to transmit torque by a frictional force generated at the contact portions between the pulleys and the chain.
As the power transmission chain, JP-A-2006-242374 proposes a power transmission chain including a plurality of links each having front and rear insertion through holes through which pins are inserted and a plurality of first pins and a plurality of second pins which are arranged in a line for connecting together the links which are arranged in a chain width direction such that the front insertion through hole of one link is associated with the rear insertion through hole of another link, a longitudinal bending of the links being enabled through relative rolling contact movement of the first pins which are fixed in the front insertion through hole of one link and fitted movably in the rear insertion through hole of another link and the second pins which are fitted movably in the insertion through hole of one link and fixed in the rear insertion through hole of another link, and wherein to reduce noise by differentiating a biting timing of the pins into the pulley, two or more pin rolling contact surface shapes and pin contact positions with the pulley surface (offset amounts) are used.
In the power transmission chain disclosed in JP-A-2006-242374 above, although noise can be reduced by combining the plurality of links which are different in pitch length and the pins which are different in shape, being at random in pitch (being at random in link arrangement) often increases a rotational angle change (wow, flutter) which causes noise, and when the pulley radius of the continuously variable transmission becomes a minimum operation radius, a total number of pins which are held between the sheave surfaces is reduced. Because of this, when the number of long links becomes relatively large under this condition, such an increase in the number of long links sometimes becomes disadvantageous in terms of durability. Conventionally, a proper arrangement of long links in a minimum operation radius of a pulley has not been taken into consideration.